It has been shown that changes in blood glucose can be sensed with an RF antenna made from silicon carbide (SiC) operating at 10 GHz. Therefore a SiC antenna patch could operate as an active sensor or as a passive sensor at 5.8 GHz for a continuous glucose monitoring system. The properties of SiC make this material ideal for biomedical applications and devices as it is not only biocompatible but also has great sensing capability. The permittivity and conductivity of the blood is glucose dependent. Thus implanting the antenna in the fatty tissue facing the muscle and blood results should result in a shift of the resonant frequency of the antenna with glucose levels. In the active sensor approach, a power supply and internal in-vivo circuitry with protection would be required. In the passive sensor approach, external circuitry sends a signal to the implanted antenna and is received back again, detecting any signal variations. Simulations in HFSS™ show that that an implanted sensor placed 2 mm from the muscle in fatty tissue would experience an approximate shift in resonant frequency of 12.3 MHz for a blood glucose change of 500 mg/dl.

The U.S. Department of Energy (DOE)’s SunShot Initiative is a collaborative national effort to reduce the price of solar energy to 6¢/kWh without subsidy for utility scale installations by 2020. Thin-film photovoltaics offer a promising path to reach this goal. Analysis of the levelized cost of energy (LCOE) from photovoltaics (PV) highlights the dependence on the module and system efficiency and lifetime in addition to module price. Here we summarize challenges and opportunities for CdTe and CIGS PV research and show that a substantial effort is still needed in areas such as device design and material improvement to reach higher efficiency and reliability connected with low-cost and robust module-scale implementation. We also discuss how SunShot Initiative funding is addressing key research areas in CdTe and CIGS PV and show how recent progress in SunShot projects is guiding funding priorities in thin-film PV research.

Novel multi-stage adaptive morphing of a hydrogel cube has been achieved by combining multi-metal ionoprinting and redox chemistry of iron. A demonstration of the two-stage deployment has been shown for (1) the selective opening and closing of the cube’s lid, where the hinge point has been ionoprinted with iron, and (2) the full unfolding and folding of the cube into its cruciform net, with remaining hinges ionoprinted with vanadium. The selective unfolding and folding is achieved by alternating the oxidation state of iron between +2 and +3. This is achieved using redox chemistry selective for iron. This approach could be applied, in principle, to more degrees of staging by adding additional redox responsive ionoprinted cations and appropriate selection of reducing agents.

It is known that photonic crystals can be used to suppress spontaneous emission. This property of photonic crystals has been investigated for suppressing and decreasing the propagation of photons within loss cones in fluorescent collectors. Fluorescent collectors can concentrate light onto solar cells by trapping fluorescence through total internal reflection. In an ideal fluorescent collector the major obstacle to efficient photon transport is the loss of photons through the top and bottom escape cones. One possible method to decrease this loss and improve the efficiency of these devices is to fabricate one-dimensional photonic crystals doped with fluorescent molecules. If these photonic crystals are tuned to exhibit a photonic band gap in the escape cone directions and at the emission frequencies of the fluorescent molecules, a suppression of the escape cone emission and an enhancement of the edge emission is expected. In this paper, we detail the fabrication of a one dimensional integrated photonic collector and show the suppression of the escape cone emission. This suppression of the escape cone will be shown to correspond to the photonic band gap and the modifications to the edge emission will be shown to correspond well with so called Fabry Perot modes. The control of emission inside fluorescent collectors opens up a number of additional possibilities for efficiency enhancements that will also be discussed.

Molybdenum based alloy having a nominal composition Mo–0.5Ti–0.1Zr–0.02C (wt%) popularly known as TZM alloy possess high temperature strength, high creep resistance, low coefficient of thermal expansion and high thermal conductivity. Processed TZM alloy contains TiC, ZrC and complex carbides which inhibit recrystallization at high temperatures and also improve the working conditions. In this study, the effect of sintering temperature, holding time and pressure on densification, microstructure and hardness of the spark plasma sintered TZM alloys were investigated. The sample sintered at 1575 °C for 150 second under 40 MPa exhibited the highest relative density, ∼98%. Microstructural characterization was performed by using FESEM and it was observed that TiC and ZrC dispersed through the microstructure. The average size of precipitates were measured as 7.5 and 3.5 µm for TiC and ZrC, respectively.

In the present work, sodium titanate nanotubes doped with potassium weresynthesized by the Kasuga method and tested as catalysts for biodieselproduction. Potassium was added to the nanotubes in order to increase theirbasicity and, consequently, improve their performance in the transesterificationof soybean oil with methanol. In the synthesis, the NaOH:KOH molar ratio waschanged from 9:1 to 7:3 in order to increase potassium loadings in the obtainednanotubular solids. Synthesized catalysts were characterized by N2physisorption, powder XRD, scanning electron microscopy (SEM-EDX), transmissionelectron microscopy (TEM), FT-IR, FT-Raman and CO2temperature-programmed desorption (CO2-TPD). Obtained results showedthat sodium trititanate nanotubes containing 1.5 wt. % of potassium wereobtained when 10 M alkali solution with NaOH:KOH molar ratio of 9:1 was used. Inthis case, the proportion of sodium and potassium in the synthesized materialwas similar to that used in the synthesis. An increase in the proportion of KOHto 20 and 30 molar % in the NaOH-KOH solutions used in the synthesis allowedobtaining titanate nanotubes with larger potassium loadings (3.2 and 3.3 wt. %,respectively). As it was expected, potassium addition to the sodium titanatenanotubes resulted in an increase in the amount of medium and strong basicsites. Potassium-containing nanotubes showed higher catalytic activity in thetransesterification reaction than the pure sodium counterpart used as areference. The best results were obtained with the samples containing 3.2-3.3wt. % of potassium where a biodiesel yield of about 94-96 % was obtained at 80°C and 1 h reaction time.

Microstructured polymeric surfaces capable of a thermally-induced shape-memory effect (SME) can perform on demand changes of surface properties such as wettability or adhesion.

In this study, we explored the influence of the applied compression direction during programming, i.e. vertical compression and tilted compression, on the SME of microstructured crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) films comprising arrays of micro-cylinders with a height of 10 µm and different diameters of 10 µm, 25 µm, and 50 µm. The shape recovery of the microstructures during heating was visualized online by optical microscopy, while atomic force microscopy (AFM) was utilized to investigate the temperature-induced shape change of single micro-cylinders. Here, the changes in micro-cylinder height and the characteristic angle θ were followed and analyzed for quantification of the shape-memory performance. Both compression modes resulted in almost flat programmed surfaces as indicated by high shape fixity ratios of Rf ≥ 93±1%. A nearly complete recovery of the micro-cylinders was obtained for all investigated cPEVA samples documented by high shape recovery values of Rr ≥ 97±1%, while the obtained shape change of the micro-cylinders during recovery almost reversely recalled the applied deformation during programming. The presented capability of SMP microstructured substrates to memorize the way of deformation during programming could be a new tool for controlling particular shape changes of microstructures during recovery and in such a way the generated local recovery forces can be adjusted.

Transition metal oxide thin film heterostructures have garnered increasingresearch interest in the last decade due to their multifunctional properties,such as ferromagnetism and ferroelectricity, which may be utilized in nextgeneration device applications. Many previous works reported on the depositionof such structures on oxide substrates such as SrTiO3, which are notcompatible with CMOS applications where Si(100) is the mainstay substratematerial. BiFeO3 (BFO) is a room temperature insulating ferroelectricand antiferromagnet, a well-known multiferroic material. SrRuO3 (SRO)is a ferromagnetic metal with the Curie temperature (TC) of 165K.Unexpected properties emerge when these two dissimilar materials are conjoined.However, there has been no report on exploring the magnetic properties of BFOwhen it is in contact with SRO, and particularly when they are integrated withSi(100) substrates, which is the subject of present study. BFO/SRO thin filmshave been epitaxially grown on Si (100) substrates by introducing MgO/TiNepitaxial buffer layers using pulsed laser deposition. BFO thin films show roomtemperature ferroelectricity as observed from piezo force microscopy (PFM)measurements. The magnetic data collected from BFO thin films show typicalantiferromagnetic features as expected. The TC of SRO in all thesamples studied was found be ∼ 170K, close to the reported value of165K. Interestingly, we have noticed that the coercive field of SRO layerincreased from 4 kOe to 15 kOe (nearly fourfold) by reducing its thickness from180 to 23nm, while keeping the thickness of BFO layer constant at 100nm. Pinningof Ru ions by ferroelectric domain walls in BFO, strong interfacial exchangecoupling and SRO layer thickness could cause the observed enhancement incoercivity. Our near future work will address the precise underlying mechanismsin greater detail.

TDDFT in real-space and real-time approach has been applied to study the optical property of poly(9,9'-dioctyl-fluorene) in the gas phase and in the solid state in order to clarify the effect of aggregation on the spectrum. We show that the spectrum of polymer chain is basically the same in linear and helical shape when it is in the gas phase, however, in solid state phase, the spectrum of aligned aggregate model is different from the spectrum sum of its constituent single chains, suggesting the existence of inter-chain interaction and its effect on the spectrum.

Multilayered film stacks, with length scales less than 10 nm are commonly used in a variety of devices, but present significant challenges to mechanical testing and evaluation. This is due to property convolution of the different layers. Both the properties of the individual layers and the combined response of the film stack are important input for design optimization. Here, we present ex-situ nanoindentation of a film stack representative of a perpendicular magnetic recording (PMR) hard disc drive (HDD), with more than 10 layers. We then compare this with in-situ transmission electron microscopy indentation to visualize deformation of individual layers of the stack. The ex-situ testing reveals early plastic deformation, with an initially high contact pressure (13 GPa) and modulus ( >160 GPa), followed by significant softening (8 GPa contact pressure and 140 GPa modulus), then slight hardening to 9 GPa. From in-situ testing, it is revealed that the metallic layer directly under the diamond like carbon (DLC) contributes the majority of the deformation and plastic flow, which is in turn constrained by a metallic oxide.

Ferromagnetic (FM) electrodes chemically anchored with thiol functionalizedmolecules can yield novel molecular spintronics devices (MSDs). However,significant challenges lie in developing commercially viable MSD fabricationapproach utilizing FM electrodes. A practical MSD fabrication approach shouldconsider FM electrodes’ susceptibility to oxidation, chemicaletching, and stress induced deformations during fabrication and usage. Thispaper will discuss NiFe, an alloy used in the present day memory devices andhigh-temperature engineering applications, as a candidate for FM electrode andfor the fabrication of MSDs. Our spectroscopic reflectance studies show thatNiFe starts oxidizing aggressively beyond ∼90 ⁰C. The NiFesurfaces, aged for several months or heated for several minutes below∼90 ⁰C, were suitable for chemical bonding with thethiol-functionalized molecules. NiFe also demonstrated excellent etchingresistance in widely used dichloromethane solvent for dissolving moleculardevice elements. NiFe also reduced the mechanical stress induced deformities inother FM metals like cobalt. This paper also discusses the successfulutilization of NiFe electrodes in the magnetic tunnel junction based moleculardevice fabrication approach. This research is expected to address the knowledgegap blocking the experimental development of FM based MSDs.

Polyphenol in mango seed kernel extraction has been demonstrated to show benefits against skin disorders. In this study, micro-cellulose sponges (MCS) from waste cotton are used as the carrier for polyphenol to produce a controlled release system. Polyphenol loaded micro-cellulose sponges were produced by acid hydrolysis and a freeze drying method. The microparticles were characterized in terms of size and morphology, total polyphenol loading, and physical state of the encapsulated polyphenol. Polyphenol release from the microparticles was assessed by dissolution tests. The particles had spherical shapes with amorphous form. The controlled drug release was tested by using different polyphenol concentration. The results showed that the structure of micro-cellulose sponges, the media type and the solubility of the polyphenol influenced the polyphenol-release behavior. Since the release of the polyphenol is controlled by the structure and interactions between the microparticles and the cellulose matrix, modulation of the matrix formers enable a control of the drug release rate. These structures of micro-cellulose sponges can be very useful in many pharmaceutical micro-particle applications.

Contact metallization is an essential obstacle for utilizing low temperature achievable polycrystalline ZnO in any discrete devices and integrated circuits. To develop ZnO based semiconductor devices with advanced feature of flexibility, transparency and compatibility with low temperature processing, rectifying junctions must be fully developed. In this work, nanoscale polycrystalline ZnO thin films are fabricated with via low temperature (<200 °C) by atomic layer deposition (ALD). A vertical structure of bottom Schottky metallized diode is developed with copper (Cu) sputtered in room temperature. A control of Cu surface oxidation is realized with an in-situ remote plasma treatment. The results indicate that preparation of the copper surface substantially affects the electrical behavior of the diode. Thermal reliability of Cu metallized Schottky diode is subsequently carried out by annealing up to a maximum temperature of 300 °C before it breaks. This work considers the current transport mechanism evolved deviating current vs voltage (I-V) characteristics from conventional thermionic emission theory.

Intrinsically conductive polymers have received increased attention in the biomedical field due to their mechanical flexibility, electronic and ionic conductivity. On the other hand, bio-derived polymers such as silk proteins (fibroin and sericin) are an important set of materials to realize mechanically deformable, biocompatible and biodegradable systems. Here, we show a ‘green’ approach to fabricate micropatterned, flexible biosensors using photoreactive silk proteins in conjunction with conductive polymers. A functional ink comprised of poly(3,4-ethylene dioxythiophene: poly(styrene sulfonate) (PEDOT:PSS) with silk sericin as a carrier enables the formation of high resolution conducting micropatterns on a silk fibroin substrate via photolithography. The flexible and conformable organic device formed can be used to sense biomolecules with high sensitivity and selectivity. The micropatterned functional silk composites are made using an all water-based fabrication approach, and shown to be cell friendly and degradable. Such systems can find applications in implantable optical devices, bio-sensors, and bio-optoelectronic devices.

We describe a simple and inexpensive method to enhance the sensitivity or improve the detection limit of solution-phase localized surface plasmon (LSPR) sensors of metallic nanoparticles. The substrate surface contains metallic nanostructures which are replicated from DVD disks via the standard soft lithography. By mixing BSA molecules with nanoparticle solution, we demonstrate that the wavelength shift due to the absorption of BSA molecules on nanoparticle surfaces is amplified by more than an order of magnitude in comparison to that over a smooth flat surface.

A variety of Titanium dioxide (TiO2) phases and nanostructures have been explored for their applications in photoelectrochemical cells (PECs) for solar-driven water splitting. In this case, anatase phase and TiO2 nanotubes offer significant advantages especially for PEC-based applications. Though, significant efforts have already been engaged to combine the advantages from both the fields, poor activation and the high electron-hole pair recombination rate of TiO2 electrodes, originating from intrinsic physicochemical properties, limits its practical use. As an alternative, we report directly grown TiO2 nanotubes (synthesized on Fluorine doped Tin Oxide (FTO) via facile electrospinning technique) on carbon nanofibers, using hydrothermal method. The hierarchical branch type configuration has an intimate contact between the TiO2 nanotube and carbon nanofiber backbone and offers higher photocatalytic activity than their respective individual components (namely TiO2 nanotubes and carbon nanostructures).

Resistive Random Access Memory (RRAM) is a novel form of non-volatile memory that is expected to play a major role in future computing and memory solutions. It has been shown that the resistance of RRAM devices can be precisely tuned by modulating switching voltages, by limiting peak current, and by adjusting the switching pulse duration. This enables the realization of novel applications such as memristive neuromorphic computing and neural network computing. The RRAM devices described in this work utilize an inert tungsten bottom electrode, hafnium oxide based active switching layer, a titanium oxygen exchange layer, and an inert titanium nitride top electrode. Linear sweep and controlled pulse (down to 10 ns) based electrical characterization of RRAM devices was performed in a 1 transistor 1 RRAM (1T1R) configuration to determine endurance, reliability, retention and threshold voltage parameters. We demonstrated endurance values above 108 cycles with an average on/off ratio of 15 and pulse voltages for set/reset operation of ±1.5V. The on-chip 1T1R structures show an excellent controllability with respect to the low and high resistive state by manipulating the peak current from 75 up to 350µA we were able to achieve 10 discrete resistive states. Our results demonstrate that the set operation (which shifts the RRAM device from the high to the low resistance state) is only dependent on the voltage of the switching pulse and the peak current limit. The reset operation, however, occurs in an analog fashion and appears to be dependent on the total energy of the applied switching pulse. Pulse energy was modulated by varying the peak voltage which resulted in a larger relative change of the RRAM device resistance.

We conducted the in-situ observations of the magnetic domain structure change inNd-Fe-B magnets at high temperature by transmission electron microscopy (TEM) /Lorentz microscopy with applying an external magnetic field. Prior toobservation, a thin foil was magnetized by an external magnetic field of 2.0 Tto almost saturation, then the magnetic domain structures were observed by theFresnel mode with in-situ heating. At 225°C, reverse magnetic domainswere found to generate in the thin foil sample without applying an externalmagnetic field. When we applied a magnetic field on the same direction to thepre-magnetization direction at 225°C, one magnetic domain wall waspinned by a grain boundary and the other magnetic domain wall moved. As theresults, the reverse magnetic domain shrank then annihilated. When we cut theapplied magnetic field, the reverse magnetic domain generated at almost the samelocation. On the other hand, when we applied a magnetic field to the foils inthe opposite direction, the reverse domain started to grow, i.e., magneticdomain walls started to move. The observation results of the shrink or growth ofthe reverse domain showed that the pinning effect of grain boundary againstdomain wall motion would be different depending on the applied magnetic fielddirection. Moreover, domain walls was observed to be pinned by grain boundariesat elevated temperature, so that the coercivity of Nd-Fe-B magnet would occur bypinning mechanism.

Water-stable CdSTe quantum dots were synthesized under microwave irradiation heating conditions. An aqueous telluride solution (produced by reducing metallic Te with NaBH4), cadmium sulphate and thioglycolic acid were mixed together in an oxygen-free atmosphere to prevent oxidation of the telluride species. The reaction temperature varied from 60° C to 180° C and was controlled by using a microwave reactor (1,000 W) to control nucleation rate and tune the size of the quantum dots. Photoluminescence analyses of resulting quantum dots evidenced a red shift (from 490 nm to 640 nm, using an excitation wavelength of 380 nm) when the reaction temperature was increased, which suggested crystal growth. The variation in size was also evidenced by the color of the quantum dot suspensions that changed from blue to red, when excited with a 405 nm, 5mW diode laser. The highest quantum yield was observed for quantum dots synthesized from 120° to 150° C. X-ray diffraction analyses suggested the formation of a solid solution of CdSTe with average crystallite size ranging from 1.4 nm to 3.2 nm. FT-IR spectroscopy evidenced the presence of residual thioglycolic functional groups onto the crystals surface, whereas HRTEM confirmed the nanometric size of the quantum dots.